Pressure vessel

ABSTRACT

This invention relates to a pressure vessel and more particularly to a pressure accumulator of the type including a rigid container having a pair of ports at its respective ends with a deformable partition or bladder therein having a mouth at one end affixed to one of said ports, said bladder separating two fluids such as gas or liquid under pressure in said container. The bladder is of the type formed from two separate sections, each substantially cup-shaped, so that when the rims of the sections are joined, a closed container will be formed. As the bladder expands to force liquid from the other port of the container, stress will be imparted to the wall of the bladder as a result of the stretching thereof, and such bladder wall is conformed to minimize the stress that would otherwise be imparted to the junction between the two sections of the bladder.

United States Patent Mercier 1 Aug. 20, 1974 PRESSURE VESSEL PrimaryExaminer-Jerry W. Myracle [76] Inventor: Jacques H. Mercier, 49 Rue deAttorney, Agent, Firm-Arthur Naples, Paris, France [57] ABSTRACT [22]Flledl Feb. 9, 1972 Appl. No.: 224,801

[30] Foreign Application Priority Data Mar. 4, 1971 France 71.7427

[52] US. Cl. 138/30 [51] Int. Cl. 1. F161 55/04 [58] Field of Search138/30; 92/98 D [56] References Cited UNITED STATES PATENTS 3,067,77612/1962 Love 138/30 3,212,446 10/1965 Golden et al.

3,408,731 11/1968 Mercier 1123.437 12/1951 Mercier 138/30 This inventionrelates to a pressure vessel and more particularly to a pressureaccumulator of the type including a rigid container having a pair ofports at its respective ends with a deformable partition or bladdertherein having a mouth at one end affixed to one of said ports, saidbladder separating two fluids such as gas or liquid under pressure insaid container.

The bladder is of the type formed from two separate sections, eachsubstantially cup-shaped, so that when the rims of the sections arejoined, a closed container will be formed.

As the bladder expands to force liquid from the other port of thecontainer, stress will be imparted to the wall of the bladder as aresult of the stretching thereof, and such bladder wall is conformed tominimize the stress that would otherwise be imparted to the junctionbetween the two sections of the bladder.

5 Claims, 5 Drawing Figures PATmIinAuczoisu SHEET 2 0f 2 Flt-2.3

PRESSURE VESSEL As conducive to an understanding of the invention, it isnoted that a conventional pressure accumulator generally includes arigid container having a pair of 5 ports at its respective ends, andhaving a deformable partition in the form of an elongated bladder havinga mouth at one end secured to one of said ports and separating twofluids such as gas and liquid under pressure charged into theaccumulator.

To facilitate manufacture of the bladder, it is desirable that it beformed from two substantially cupshaped sections, one of the sectionshaving a gas fitting molded at the end thereof and extending axiallytherefrom, the rims of the two cup-shaped sections being securedtogether in any suitable manner, such as bonding by hot or coldvalcanization or by the use of adhesives with or without heat treatment.For facility in describing the invention, such connected junctionbetween the two rims will be hereinafter referred to as the bonded zone.

In addition to the bonded zone being at the junction of the two rims ofthe bladder sections, the invention may also be applied to the bondedzone at the junction of a valve member, particularly a rigid button, tothe end of the bladder, which valve member cooperates with the liquidport of the pressure vessel.

The bladder of a pressure accumulator is designed to be charged with gasunder pressure and to react against a liquid such as oil charged intothe container through the liquid port so that when the port issubsequently opened, the bladder will expand to force the liquid out ofthe liquid port to actuate the components of the hydraulic system inwhich the pressure accumulator is utilized.

It is apparent that since the bladder normally, in its inflated butundistended condition, is of length considerably shorter than thecontainer to prevent premature closing of the liquid port before all ofthe liquid in the container is forced therefrom, as the bladder expandsin use, the wall thereof will be subjected to considerable stress andsuch stress will of course be imparted to the bonded zone above referredto.

Since the bonded zone in fact forms a discontinuity in the integral wallof the bladder, in order to strengthen the bonded zone it would benecessary to increase the surface area of the bond and to use a cementor other means of adhesion that is as strong as possible.

Unfortunately, due to the physical size of the bladder wall, it is notalways possible or desirable to have a bonded zone covering a largearea.

Thus, where the bonded area involves the adjacent rims of two sectionsof the bladder, these rims can be bevelled so as to define an obliquebonding area.

Obviously, the bonded area can be increased by bev elling such rims sothat the bevelled parts extend almost parallel to the wall of thebladder. However, manufacturing limitations do not generally permit abonded area with surfaces almost parallel to the wall of the bladder andin practice the slope of the abutting rims is based on the physicalconfiguration of the bladder wall itself.

In addition, where the bonded zone is formed between the bladder andanother element such as a valve member, the dimensions of the bondedarea is based upon the area of the valve member, for example, which isavailable for bonding.

Furthermore, it is not always possible in many applications to use veryhigh performance adhesives or cements since the material from which thebladder is made, such as natural rubber, or plastics, may not becompatible with such cement or adhesives and in addition it may not becompatible with the particular liquid being used in the accumulator.

Furthermore, the cost of adhesives that might be compatible might beprohibitive.

It is accordingly among the objects of the invention to provide abladder for use in a pressure vessel, which has a bonded zone that issubjected to stress during operation and which bladder is conformed tominimize the stress imparted to such bonded zone without need for havinga bonded zone of large area or employ an adhesive or bond of highperformance.

According to the invention, a partition or bladder is positioned in arigid container to separate two fluids therein and is affixed in thecontainer in such manner that the bladder defines two chambers for suchfluids.

The bladder has a bonded zone which is formed either by the junction oftwo sections of the bladder or by the junction of a valve member to thebladder.

The wall of the bladder adjacent the bonded zone has a stress reliefzone which at least partially relieves the bonded zone from stressesthat would otherwise be applied thereto during operation. Moreparticularly, such stress relief is accomplished by a reduction of thethickness of the bladder wall.

According to the one embodiment of the invention, the width of thestress relief zone is at least equal to that of the bonded zone and thedistance separating said zones is less than twice the width of thebonded zone to be protected.

As a result of the above arrangement, the stress on the bladder wallresulting from expansion of the bladder during operation will beprimarily absorbed by the stress relief zone due to its reducedthickness.

Consequently, the area of the bonded zone is not critical and the bondmaterial used need not be of a high performance high cost material, butonly need satisfy the condition that it is compatible with the materialof the bladder and the liquid used in the pressure vessel.

In the accompanying drawings in which are shown one or more of variouspossible embodiments of the several features of the invention;

FIG. 1 is a longitudinal sectional view of a pressure accumulatoraccording to the invention in which the bonded zone to be protected islocated between two sections of the bladder.

FIG. 2 is a view similar to FIG. 1 of another embodiment of theinvention in which the bonded zone to be protected is located betweenthe bladder and a valve member;

FIG. 3 is a detail view of an enlarged scale showing the bonded zone andrelief zone of FIG. 2;

FIG. 4 is a detail view on an enlarged scale showing the bonded zone andrelief zone of FIG. 1, and

FIG. 4a is a schematic representation in rectilinear development of theportion of the bladder shown in FIG. 4 during expansion thereof.

Referring now to the drawings, there is shown in FIG. 1 a pressureaccumulator comprising a rigid container of steel or aluminum, forexample, capable of withstanding relatively high pressure. The container10' has a cylindrical body portion with substantially hemisphericalends, each having a port 11 and 12. The ports 11 and 12, which areaxially aligned, define a gas port and a liquid port respectively.

Positioned in the gas port is an externally threaded fitting 13 whichhas an axial bore therethrough, said fitting having an annular flange Fat its inner end and protrudes outwardly from said port 11. A nut 13ascrewed on the protruding end of said fitting 13 securely retains thelatter in said port 11.

A deformable separator, illustratively a bladder 15 of rubber or similarmaterial having like characteristics, is positioned in said container10, to divide the latter into two chambers 16 and 17. One of thechambers 16 defines a gas chamber which is in communication with thebore of fitting 13, the bore having a conventional valve V such as aSchrader valve at its outer end, for charging of the chamber 16 with gasunder pressure.

The bladder 15 has a mouth 14 which is secured as by bonding to theannular flange F of fitting 13.

The port 12 releasably mounts a poppet valve assembly comprising asleeve 18 which protrudes outwardly from port 12 and is internallythreaded as at 18' for connection to the hydraulic system with which thepressure accumulator is associated. The inner end of sleeve 18, whichprotrudes into the container, is beveled at 21 to define a seat for thepoppet valve 19, the latter normally being urged away from its seat bycoil spring 20 and being designed to be moved against the seat 21 whenthe bladder expands.

In operation, gas under pressure is forced through valve V to charge thechamber 16 with a predetermined pre-load. As a result, the bladder 15which in inflated but undistended condition, is of size smaller than thecontainer 10, will expand against the entire inner surface of thecontainer 10 and close the valve 19.

A liquid such as oil is then introduced through the bore 18 of sleeve 18under a pressure greater than the pre-load pressure in bladder 15causing the latter to compress the gas contained in chamber 16.Thereupon a valve (not shown) positioned between sleeve 18 and thehydraulic system is closed. Thus, chamber 17 will contain a volume ofoil under high pressure which is available for use when such valve isopened.

As the construction and operation of the pressure accumulator thusdescribed is conventional and well known to those skilled in the art, itwill not be further described except as is necessary for a clearunderstanding of the invention.

From the above description, it is apparent that the bladder 15 will besubjected to stresses, particularly when it expands and stretches toforce oil from the container.

In the embodiment shown in FIGS. 1 and 4, the bladder is relatively longand is formed from two sections 15a, 15b joined as at 22. Moreparticularly, the sections 150 and 15b are substantially cup-shaped andthe junction 22 at which they are joined, is in the form of an annulusor band whose width measured along the axis of container 10 is shown atA in FIGS. 1 and 4.

As is clearly shown in FIG. 4, adjacent rims of the sections 15a, 15bare bevelled as at 22a, 22b and the juxtaposed faces 22a, 22b which arecomplementary, are bonded or cemented together to form a bonded zonethat extends obliquely. Such inclination of the junction 22 affords agreater bonding area than would be present if the rims of section 15a,151; were parallel to each other in a plane perpendicular to the axis ofthe bladder.

The junction or bonded zone 22 between the two rims 22a, 22b may beformed in any suitable manner, such as bonding by hot or coldvulcanization or by the use of adhesives with or without heat treatmentor the like.

The bonded zone 22 must resist the force or stress applied theretoduring movement of the bladder 15 and particularly during expansion orstretching of the bladder 15 which tends to pull the surfaces 22a and22b away from each other, the form of the bladder when it stretchesbeing shown schematically in FIG. 4a.

According to the invention, the bladder 15 as is shown in FIGS. 1 and 4,is provided with a stress relief zone 23 adjacent the bonded zone 22 tobe protected, the function of the zone 23 being to absorb the majorityof the stretch imparted to the bladder wall during expansion thereof sothat a minimum amount of stretch will be imparted to the bonded zone 22.

The stress relief zone 23 is formed by reducing the thickness of thebladder wall and for the stress relief zone to be effective it must beof substantial dimensions.

More particularly, as is clearly shown in FIGS. 1 and 4, the width ofthe bonded zone 22 is identified by the letter A along the longitudinalaxis of the bladder.

The width of the stress relief zone 23 is identified by the letter C"along the longitudinal axis of the bladder and the distance separatingthe zones 22 and 23 is identified by the letter B along the longitudinalaxis of the bladder.

In the preferred embodiment shown, the width C of the stress relief zoneis at least equal to and preferably greater than the width A of thebonded zone 22 to be protected and as shown, the width C isapproximately four times the width of A.

It is desirable that the stress relief zone 23 be relatively close tothe bonded zone 22 so that it can be more effective in relieving thestress. In practice it has been found that efficient results areobtained when the distance B along the longitudinal axis of the bladderseparating the zones A and C is slightly less than twice the width ofthe zone A and in the illustrative embodiment shown, the width B isapproximately 1.7 the width A.

As shown in FIGS. 1 and 4, the reduction in thickness of the portion ofthe bladder wall that forms the stress relief zone 22, is gradual fromthe extremities 15" of this zone 23 to its mid-portion e, alsodesignated by the reference numeral 24, where the thickness of thebladder wall is approximately one-third or one-half the thickness of thebladder wall E.

As a result of such gradual reduction in thickness, there is asubstantial wall thickness at e, so that likelihood of tearing of thebladder while stretching is substantially precluded.

Thus, in operation of the pressure accumulator, according to theinvention, as the bladder 15 expands, due to the reduced wall thicknessat the stress relief zone 23, the bladder wall will stretch more at suchzone than at the remaining portions thereof, so that the stress on thebonded surfaces 22a and 22b will be minimized.

In the embodiment of the invention shown in FIGS. 2 and 3, elementssimilar to those in FIGS. 1 and 4 have the same reference numeralsprimed.

Referring to FIGS. 2 and 3, the bladder 15 is positioned in a rigidcontainer having a gas port 11' at one end and a liquid port 12 at itsother end.

The bladder 15' mounts a valve member 25 at its free end, which valvemember is designed to move against annular seat 26 to close the port 12when the bladder expands in use.

The valve member 25 is bonded as at 22' to the end of the bladder, sucharea 22' being the bonded zone identified by the letter A.

The end of the bladder has a stress relief zone 23 also identified bythe letter C, the thickness of the bladder wall being more at the endsE' of zone 23 than at the mid portion e' of said zone 23' identified bythe numeral 24.

As described with respect to the embodiment of FIGS. 1 and 4, the stressrelief zone 23' of FIGS. 2 and 3 serves to relieve the bonded zone 22from the stress resulting from expansion and stretching of the bladderin use.

In the embodiment of FIGS. 2 and 3, the width or distance C is slightlygreater than the distance A while the width or distance B isapproximately one-third of the distance A.

The wall thickness of the bladder at e is approximately one-third orone-half the wall thickness at E.

The reduced thickness of the bladder wall can be in a symmetrical manneras shown in FIGS. 1 and 4, or in an offset manner as shown in FIGS. 2and 3, in which the thinning is on the inside of the bladder, but it canalso have any other suitable configuration.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A pressure vessel comprising a rigid hollow container having axiallyaligned ports, a partition of resilient deformable material in saidcontainer intervening between said ports and defining two chambers incommunication respectively with said ports, said partition having a bondzone subject to the stresses imparted to the partition as a result ofthe stretching thereof in operation, characterized by said partitionhaving in proximity to said bond zone, a stress relief zone, the widthof said stress relief zone being at least equal to that of the bond zoneand the distance separating said zones being less than twice the widthof said bond zone, said stress relief zone being adapted substantiallyto absorb the stresses resulting from stretching of the partition, towhich the bond zone would otherwise be subjected, said partition havinga reduced wall thickness defining said stress relief zone, the lattercomprising a decreasing thickness zone spaced from the bond zoneimmediately followed by an increasing thickness zone, the thickness ofthe portion of the partition wall defining said stress relief zone beinggradually reduced from the extremities of the zone to the middle portionthereof, the thickness of the partition wall at the middle portion ofthe stress relief zone being between onethird to onehalf the thicknessof the partition wall at the extremities of said stress relief zone.

2. The combination set forth in claim 1 in which said partition is abladder having two substantially cupshaped sections one of said sectionshaving an axial opening at its end, means connecting the rims of saidsections to define said bond zone therebetween, the other of saidsections being of reduced wall thickness starting from a portion of saidsection longitudinally spaced from the bond zone, to define the stressrelief zone, the latter being of width approximately four times thewidth of the bond zone.

3. The combination set forth in claim 1 in which the distance betweenthe bond zone and the stress relief zone is approximately 1.7 times thewidth of the bond zone.

4. The combination set forth in claim 1 in which the width of the stressrelief zone is slightly greater than that of the bond zone and thedistance separating said zones is approximately one-third the width ofsaid bond zone.

5. The combination set forth in claim 1 in which said partition is abladder having a mouth at one end in communication with one of saidports and closed at its other end, a valve member bonded to the closedend of said bladder, the area of the bond of said valve member to saidbladder defining the bond zone.

1. A pressure vessel comprising a rigid hollow container having axiallyaligned ports, a partition of resilient deformable material in saidcontainer intervening between said ports and defining two chambers incommunication respectively with said ports, said partition having a bondzone subject to the stresses imparted to the partition as a result ofthe stretching thereof in operation, characterized by said partitionhaving in proximity to said bond zone, a stress relief zone, the widthof said stress relief zone being at least equal to that of the bond zoneand the distance separating said zones being less than twice the widthof said bond zone, said stress relief zone being adapted substantiallyto absorb the stresses resulting from stretching of the partition, towhich the bond zone would otherwise be subjected, said partition havinga reduced wall thickness defining said stress relief zone, the lattercomprising a decreasing thickness zone spaced from the bond zoneimmediately followed by an increasing thickness zone, the thickness ofthe portion of the partition wall defining said stress relief zone beinggradually reduced from the extremities of the zone to the middle portionthereof, the thickness of the partition wall at the middle portion ofthe stress relief zone being between onethird to one-half the thicknessof the partition wall at the extremities of said stress relief zone. 2.The combination set forth in claim 1 in which said partition is abladder having two substantially cup-shaped sections one of saidsections having an axial opening at its end, means connecting the rimsof said sections to define said bond zone therebetween, the other ofsaid sections being of reduced wall thickness starting from a portion ofsaid section longitudinally spaced from the bond zone, to define thestress relief zone, the latter being of width approximately four timesthe width of the bond zone.
 3. The combination set forth in claim 1 inwhich the distance between the bond zone and the stress relief zone isapproximately 1.7 times the width of the bond zone.
 4. The combinationset forth in claim 1 in which the width of the stress relief zone isslightly greater than that of the bond zone and the distance separatingsaid zones is approximately one-third the width of said bond zone. 5.The combination set forth in claim 1 in which said partition is abladder having a mouth at one end in communication with one of saidports and closed at its other end, a valve member bonded to the closedend of said bladder, the area of the bond of said valve member to saidbladder defining the bond zone.